let myPerson: {
    name: string; 
    age: number; 
    sayHi(name: string): void
} = {
    name: 'jack',
    age: 19,
    sayHi(name: string) {
        console.log('Sieg Heil,' + name);
    }
}

let person1: {
    name: string; 
    age?: number; 
    sayHi(name?: string): void
} = {
    name: 'black',
    sayHi(name) {
        console.log('hello ' + name);
    }
}

let person2: {
    name: String
    age: number
    siegHeil: (name?: string) => void
} = {
    name: "black",
    age: 10,
    siegHeil: (name) => {
        console.log(name + ' sieg heil')
    } 
}
person1.sayHi('black')
myPerson.sayHi("Hitter")
person2.siegHeil("while") 